Clutch assemblies comprising a housing assembly, a friction assembly disposed in the housing assembly, which friction assembly comprises a first friction surface assembly and a second friction surface assembly which can be brought into operative engagement with one another through an actuation device, are known in a plurality of embodiments. Thus, the housing assembly is typically configured as a rotating housing assembly and coupled with an input of the clutch device or it forms said input, wherein the input can be coupled with a drive unit. The first friction surface assembly is connected torque proof to the input or to the housing assembly, while the second friction surface assembly is coupled torque proof with the output. The output is formed by a transmission component, typically by a transmission input shaft, when a force transmission device is connected in front. Such clutch assemblies can be used by themselves or they can also be used in so-called force transmission devices.
Reference is made to the printed documents DE 196 22 593 C2 and DE 103 08 137 A1 with respect to combinations of clutch assemblies with hydrodynamic components in force transmission devices. An embodiment in a twin clutch assembly is described e.g. in EP 1 541 887 A1. All clutch assemblies are friction clutches which can be operated with slippage.
The friction locking is thus implemented by friction surfaces, wherein at least one friction surface is configured as a friction liner. Said liner is often comprised of organic material. In particular, during slippage operation, such clutch assemblies are exposed to high thermal loads, and therefore have to be cooled well in order to prevent burning the mostly organic friction liners. Thus, depending on the embodiment of the clutch assembly, an open cooling with a cooling medium flowing through is selected. Said type of cooling is possible for all embodiments recited supra. When integrating such a clutch assembly in a force transmission device with a hydrodynamic component, an operating means from an external loop, which is associated with the hydrodynamic component, is thus used as coolant flow.
The printed document DE 196 22 593 C2 discloses an embodiment of the force transmission device comprising a hydrodynamic speed-/torque converter, and a clutch assembly associated with said force transmission unit, which clutch assembly is provided as a lockup clutch for torque proof connection between the input of the force transmission device and the output, in particular, for torque proof coupling between the pump shell and the turbine shell of the hydrodynamic speed-/torque converter. Depending on the embodiment of the force transmission device as a two- or three channel system, the actuation device for the clutch assembly can be controlled or adjusted by the pressure in the hydrodynamic component or through a separate additional pressure cavity, which controls the contact pressure force of the actuation device, irrespective of the pressure in the hydrodynamic component. In order to remove the heat, which is created during slipping operation of the clutch assembly, thus coolant, in particular the operating means of the hydrodynamic converter, is conducted through radially configured channels, which are configured in the components forming the friction surface. The channels provided in the area of the friction zone are thus configured, so that the flow of hydraulic fluid required for cooling, in particular the flow of converter fluid, is assured. Thus, a pressure opposed to the actuation device is generated between the elements of the friction liner assembly, which can be brought into operative engagement with one another, which pressure, however, is compensated in turn by a respective configuration of the piston element. Thus, the provided channels extend completely over the entire friction zone, which channels carry fluid in particular during lockup operation, which fluid exits in radially outward direction, this means, due to the centrifugal force through the intermediary space between the pump shell and the turbine shell from the hydrodynamic speed-/torque converter, and which is routed through the cooling channels (27.1, 27.2) in the clutch assembly. Said friction zone is configured, so that the flow velocity is reduced. The routing is thus performed over the entire friction surface in the portion of the inner circumference up to the outer circumference, and the coolant exits again at the respective inner- or outer circumference and is removed. Thus, the groove patterns of the elements bearing friction surfaces and disposed adjacent to one another are configured analogous to one another.
An embodiment also routing operating means of a hydrodynamic converter through the clutch assembly, in particular from the portion of the outer circumference to the inner circumference of the clutch assembly, is known from the printed document DE 103 50 935 A1. This document discloses a method and a device for dosing an oil flow. Herein, dosing the oil flow is performed through at least one friction surface of at least one friction surface bearing element configured as a disk of a friction surface assembly of a converter lockup clutch, wherein the oil flow through the pump shell and through the stator shell is restricted by measures in the space between the outside of the turbine shell and the inside of the converter, so that the oil flow over the at least one friction surface is increased. Also here, operating means is routed from the hydrodynamic speed-/torque converter through the clutch assembly. Thus, a flow is only performed in one direction, wherein the operating means flow is performed in lockup operation, this means with the clutch assembly actuated, through integrated coolant channels in particular friction surface bearing elements of the friction assembly of the clutch assembly, and the routing is performed from the outer circumference of the hydrodynamic speed-/torque converter and back to the same or through a separate cooling system. Thus, in this embodiment, a coolant flow is formed caused by the operation of the converter in lockup mode, which coolant flow through the clutch assembly is continuous during filling. Said coolant flow can also be conducted in a loop, wherein, however, the loop paths can be very long. The particular friction surface bearing elements are thus always flowed through substantially in the same direction, and thus cooled, so that the coolest portion is disposed in the portion of the outer circumference, while the portion at the inner circumference is always flowed through by coolant with increased temperature. Thus, for optimized cooling, the cooling power, and thus the flow-through, has to be increased.
Another cooling problem, when configuring the clutch assembly as a disk clutch in a twin clutch, is known from the printed document EP 1 541 887 A1. Here, two single clutch assemblies are provided, which are coupled with a drive respectively, and furthermore, their second friction surface assembly is can be respectively connected torque proof with an output. The cooling can be performed here as a closed cooling. In this case, the clutch assembly is constantly disposed in an oil torus. Due to the viscosity of said medium, besides the cooling problem, there are also problems when activating the clutch assembly or during disengaging due to the viscosity of the oil. In this embodiment, the volume of the cooling medium surrounding the friction surface assembly is controlled by a control valve by implementing the control through a run-in and run-out to the interior cavity of the clutch assembly. In order to obtain a respective cooling effect, it is often also necessary to increase the pump power in order to provide the respective coolant volume. The particular solutions are then characterized by significant additional complexity.
Thus, it is the object of the invention to improve a clutch assembly of the type recited supra, so that it implements a local coolant loop for the friction assembly, wherein the embodiment shall be characterized by low design and manufacturing complexity. Furthermore, a closed loop for the friction assembly shall be implemented in a simple manner, which is effective only locally in the portion of the friction assembly and which flows through the particular friction surface bearing elements several times. High cooling efficiency is desired as an additional requirement.